The brush coater is the oldest coating equipment; the air knife: the advent of the coater marks the birth of the modern paper coating industry. The air knife coater overcomes the above shortcomings of the brush coater and is quickly promoted, resulting in a sharp increase in the output of coated paper. According to the different loading equipment, blade type and blade installation position, the blade coating head is also divided into many types, such as hard blade blade coater, drag blade coater, soft blade blade coater, fountain type upper Material knife coater, short residence knife coater, Bill knife coater, knife roll coater, etc. Roll coating uses a coating roller to apply paint to the coating surface, and in-machine coating is mainly based on this type of coating machine. The coating amount can be adjusted by measuring the pressure between the rollers, the pressure is strengthened, the throughput of the coating decreases, and the coating amount is also reduced.